1. Field of the Invention
The present invention relates to a levelling valve actuating apparatus for use in air suspension of a vehicle, particularly to a levelling valve actuating apparatus which is constructed between a levelling valve body and the suspension and is controlled by means of vehicular height displacement varied depending upon road conditions.
2. Description of the Prior Art
In general, an air spring used in air suspension system supports weight of the vehicles, absorbs vibration and shock resulting from the road, and reduces or attenuates irregular vibration transmitted from road wheel by means of air cushion. Thus, safe and comfortable driving is accomplished.
Such an air spring is connected to an air tank through a levelling valve. Compressed air within the air tank is introduced into the air spring through an intake port of the levelling valve or is discharged through the exhaust port of the valve.
As shown in FIG. 6, the conventional levelling valve is constructed in a manner that a rotating plate (not shown) for switching hydraulic fluid passage inside the valve body 51 is connected to one end of a lever 52 for adjusting vehicular height located outside the valve body 51, the other end of the lever 52 is disposed in a perpendicular direction to the rotating plate and hinged to an end of a rod 53 for adjusting vehicular height, and the other end of the rod 53 is connected to the suspension member 54 through a ball joint 55.
The rod 53 and the lever 52 change a vertical displacement into an angular displacement in response to vehicular height of the front/rear wheel-side varied on vehicle weight change, drive the rotating plate (not shown) within the levelling valve 56 to rotate, and control the opening/closing of intake/exhaust ports. Thus, the levelling valve 56 is actuated to maintain stable vehicular height by supplying or discharging the compressed air into or from the front/rear air springs.
However, as mentioned above, the lengths of the rod and the lever used as an apparatus for actuating the levelling valve are determined to be constant. Thus, in the case that the road condition is extremely poor and maximum displacement of the vehicular height has occurred, there is a problem that the rotating plate in the levelling valve moves beyond its rotational region, and consequently the levelling valve is erroneously actuated.
Further, another problem is that the levelling valve which may variably adjust the response of air springs depending upon the road condition cannot obtain the desired levelling due to the constant length of the rod and the lever.